The non-equilibrium populations of excited vibrational states of the CO2 molecules in the problem of radiation transfer in infrared bands of carbon dioxide in the middle and upper atmosphere of the Earth are investigated, taking into account changes in the absorption coefficient due to the line-mixing effect. To do this, a carbon dioxide molecule model is used to study non-equilibrium CO2 emissions in the Earth's atmosphere, which takes into account 206 vibrational states of the 7 isotopologues of CO2 giving rise 545 radiation vibrational transitions consisting of about 64200 ro-vibrational lines. The line-mixing effect was taken into account only for lines belonging to the spectral range of the 15 μm CO2 band, using a correction function to the values of the radiation absorption coefficient in this band, which was calculated within framework of the strong collision model with adjusted branch coupling. It is shown that taking into account the deviation of the frequency profile of ro-vibrational transitions in the spectral range of the 15 μm CO2 band from the sum of Voigt profiles due to the phenomenon of line-mixing leads to only insignificant (less than 2%) changes both in the values of non-equilibrium populations of vibrational states of CO2 excited in the bending mode of the CO2 molecule and in the magnitude of the rate of radiative cooling of the atmosphere in the bands of CO2. The study could be useful for understanding the radiation regime in planetary atmospheres. The results of the work may be used in the development of methods for remote sensing of atmospheric parameters.
Until now, a number of issues related to the energy and dynamics of the atmosphere of Venus remain unclear. In particular, this is the phenomenon of superrotation, which consists in the presence of a high-speed wind flow in a narrow high-altitude layer above the upper boundary of clouds in the equatorial atmosphere of Venus. In the framework of the simplified model, the problem of radiation transfer in the spectral lines of infrared CO2 bands in the planetary atmosphere is considered, taking into account the frequency shift of the volume opacity coefficient due to the Doppler effect. Such frequency shift occurs when there is non-zero value of projection onto the ray pathway of the velocity vector of large-scale winds. For different viewing angles, the variability of the values of the radiation intensity leaving the atmosphere at the upper boundary was studied, depending on a number of parameters of both the model of the vertical gradient of the horizontal wind speed and the spectral parameters of the line (band). The analysis of the present study results allows us to conclude that further investigations of the above mentioned radiative transfer problem for more realistic models would be fruitful.
A mechanism of excitation of the CO2 vibrational states due to E-V energy transfer through a chain O(1D) → (N2(v), v=1−5 and O2(v), v=1−4) ↔ CO2(v3) was updated in the non-LTE model for the CO2 infrared emissions in the Earth atmosphere. It was found that including this mechanism results in significant increase of populating the excited vibrational states of N2, O2 and CO2 followed by significant increase of cooling rate due to transfer of radiation in the CO2 bands in the altitude region of 90-110 km. Main inferences are as follows. For noon conditions at the equator for spring equinox under average level of solar activity (F10.7=90), about 23-25 per cent of flux of solar UV energy, which spent to excitation the O(1D) state after photodissociation of ozone and molecular oxygen, transfers to both N2(v) and O2(v) vibrational states due to E-V energy exchange during collisions. After that, a part of this flux transfers to the CO2(v3) states due to intermolecular V-V energy exchange. Finally, the energy is radiated from the atmosphere mainly in the 4.3μm fundamental band of the CO2 principal isotope with an efficiency of 0.9, 0.87, 0.82, 0.6, and 0.25 at the altitudes of 90, 95, 100, 105, and 110 km, respectively. This provides an additional cooling of the MLT region with a maximum rate of order 6.0 K/day at 105 km. Such an estimation is more larger than it had been obtained in previous investigations. So, comparing to the most recent estimations of the 15 μm CO2 band cooling rate, this seems to be a valuable additional source of cooling of the lower thermosphere comparing to the most recent estimations of the 15 μm CO2 band cooling rate.
The problem of radiative transfer in the ro-vibrational molecular bands under condition of local thermodynamic equilibrium breakdown in a planetary atmosphere is generalized for the case taking into account the extinction (i.e. scattering and absorption) of the continuum radiation produced by aerosols. The method for calculating the nonequilibrium populations of vibrational states of gas molecules in the planetary atmospheres is developed. Formation of the values of the non-equilibrium populations of the excited vibrational states of the CO2 molecules (in the application to the atmosphere of Mars) within the framework of the model of radiative transfer in the near-infrared bands of this molecule taking into account the extinction of radiation in the continuum produced by aerosol particles has been investigated for the first time. The most complete optical model of the CO2 and CO molecules is used. A distinctive feature of this model is the detailed accounting of the overlap in frequency of the lines in the spectral range of 1.05–15 μm, which belong to all ro-vibrational transitions of different isotopologues of the CO2 and CO molecules included into the optical model, as well as accounting for the reflection of radiation by the surface of the planet.
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